God's Palette

景深ΔL=ΔL1+ΔL2=(2f^2FδL^2)/(f^4-F^2δ^2L^2)

From formulas (1) and (2), it can be seen that the rear depth of field > the foreground depth.

It can be seen from the depth of field calculation formula that the depth of field is related to the aperture of the lens, the focal length of the lens, the shooting distance, and the requirements for image quality (expressed as the size of the allowable circle of confusion).The influence of these main factors on the depth of field is as follows (assuming that other conditions do not change):

(1) Lens aperture: the larger the aperture, that is, the smaller the aperture value, the smaller the depth of field; the smaller the aperture, that is, the larger the aperture value, the greater the depth of field;

(2), focal length of the lens: the longer the focal length of the lens, the smaller the depth of field; the shorter the focal length, the greater the depth of field;

(3) Shooting distance: the farther the distance, the greater the depth of field; the closer the distance, the smaller the depth of field.

(15) Color temperature

Color temperature is a measure of the light color of a light source, and the unit is K (Kelvin). It has important applications in photography, video, publishing and other fields.The color temperature of a light source is determined by comparing its color to a theoretical hot black body radiator.The Kelvin temperature at which a hot black body radiator matches the color of a light source is the color temperature of that light source, and is directly related to Planck's black body radiation law.

Different color temperatures show different colors, which directly affect the emotional expression of photos.

In addition, the white balance fixed mode on the camera is only an approximate value, such as direct sunlight, tungsten lamp, fluorescent lamp, cloudy sky, etc., but in many cases, the light source is not a simple one, there will be complex light sources, even if it is The intensity of sunlight varies in different seasons, so the color temperature needs to be fine-tuned, otherwise the color of the photo will be biased.

(16) What is a medium format camera?

120中画幅相机是指使用宽度为6cm的120/220胶卷或电子感光元件的,成像尺寸介于36×24mm的小画幅及4×5英寸的大画幅之间的相机，成像尺寸有6×4.5cm，6×6cm，6×7cm，6×9cm等。中幅相机的企业主要有哈苏、禄莱、玛米亚、宾得、富士等。

A medium-format roll film camera that sits somewhere between the lightweight 35mm compacts and single-lens reflex cameras and the bulky sheet cameras, it is the ideal model for many professional photographers.Although less bulky, these cameras used negative film larger than 35 mm and were able to produce prints and transparencies with higher resolution and tonal quality.

6 x 4.5 cm camera

Compared with other medium-format cameras, the 6 x 4.5 cm single-lens reflex film camera is relatively light in handling.This type of camera can shoot images that are 6 cm (2 inches) high (the height of the film), but only 4.5 cm (1 inch) wide. The core of the body can be equipped with a series of different handles, viewfinders, Lens and film back, more flexible than a standard 35mm SLR.

6 x 6 cm camera

This medium-format single-lens reflex film camera, also known as a 2-inch-square camera, can capture an image of 6 square centimeters (or 2 square inches).Some photographers are passionate about this type of format, while others prefer the composition of images in a rectangular format.

direct view camera

If the bulkiness of a medium format camera discourages you, consider a 6 x 6 cm direct-view camera. The rangefinder focus significantly reduces the overall size of the camera and reduces the overall weight of this type of camera.This camera is similar to a larger 35mm pocket camera, with the added advantage of increasing the size of the film image (about 4 times the size of a 35mm negative)

6 x 7 cm camera

6×7厘米照相机能拍摄6×7厘米(2×2英寸)的矩形影象，非常适合于风光摄影。在外观和操作上，它类似于一架放大了的35毫米单反机，但其通用的镜头范围没有标准的35毫米单反机那样广。而且由于镜头尺寸和产量方面的原因，其售价较昂贵。这种中幅照相机采有120或220胶卷。

6 x 9 cm camera

This film camera can capture a 6 x 9 cm (2 x 3 in) rectangular image.Large size original negative or original positive ensures high-quality enlargement.This model uses a split-image rangefinder viewfinder instead of a through-the-lens reflective viewfinder.Therefore, the weight is greatly reduced.The lenses are not interchangeable, but there are two models with different focal lengths to choose from.

(18) What is the digital back that appears with the medium format

A digital back refers to the digital imaging and processing module installed on a medium format camera.The main function of the digital back is to replace the original film back and digitize the photos.Current digital backs integrate multiple functions such as sensors, screens, memory card slots and batteries.

Most of the digital backs on the market can be installed on a series of medium-format cameras such as Hasselblad V/H series, Contax, and Mamiya. In recent years, cameras specially designed for digital backs have also appeared.

The biggest advantage of the digital back lies in the overwhelming pixel resolution and excellent imaging effect.Taking the Phase One IQ series as an example, the product line covers various levels from 8000 million pixels to 4000 million pixels, and recently launched a 3000 million pixel full-frame format digital back.

数码后背的另一个优势在于传感器尺寸。IQ160、IQ180的传感器尺寸为53.9×40.4mm，虽然入门级产品IQ140的传感器尺寸只有44×33mm但仍要大于全画幅的36×23.9mm。

In addition, ordinary SLR cameras can only output 14bit RAW files at most, while digital backs are basically above 16bit. Although there is only a 2bit difference, the naked eye can already clearly distinguish the difference in dynamic range between the two files.

Seeing this, Mian Yu fell asleep completely, and she threw this thing into the trash can.

The next day, Xia Xun threw another book to her——

It seems to be talking about the camera?

① Lens focal length

The focal length, simply put, is the variation range of the focal length of the zoom lens.

The division of the focal length of the lens: the first is the so-called standard lens.Its viewing angle is around 43 degrees, which is the closest to the perspective of the human eye.The focal length of the header is also different for different film formats. The standard lens of the 135 format is about 50mm, the focal length of the 120×6 head of the 6 is 80mm, and the head of the 300d is about 50÷1.5=33mm.Documentary photos use headers to faithfully record what you see, so most documentary photography masters like to use headers, such as French photography master Bresson.

When the focal length is smaller than the header, the lens can record images with a wider viewing angle, so it is called a wide-angle lens.The perspective of wide-angle lenses is exaggerated.Under the wide-angle lens, the closer ones are bigger and the far ones are smaller, especially in landscape photography, you can get more visually impactful photos.

A lens with a focal length 1.5 to 4 times larger than the focal length of the header is called a medium focal length.Generally, the deformation of the medium-focus lens is the smallest, and it is relatively easy to design a super-large aperture, so portrait photography is what the medium-focus lens is best at.Generally, the focal length of 1.5 to 2 times of the header is used to take photos of the whole body and half of the body.Lenses larger than 2x are mostly used for close-up shots, and several lenses known as "portrait kings" in the lens all appear in this focal length.

A lens that is more than 2 times the focal length of the head is called a telephoto lens.As the name suggests, the telephoto lens can achieve "telescopic" shooting, and is mostly used for shooting sports, animals, etc. The application of the telephoto lens in landscape films can compress the perspective of the landscape.

Standard lens: For a 135 camera, a lens with a focal length of about 50MM—the angle of view is about 43 degrees. The perspective effect of the photos taken by the standard lens is similar to that of the human eye, which is extremely natural and not exaggerated.Documentary photos use headers to faithfully record what they see, so most documentary photography masters like to use headers, such as French photography master Bresson.For cameras with different formats, the focal length of the standard lens is different, because the definition of the focal length of the standard lens means that the focal length is equal to the length of the diagonal of the film. For a 35mm film, that is, the film used by a 135 camera, its The focal length of the standard lens is 50mm, and some other large-format cameras, such as 120 cameras use 6X6 film, the focal length of its standard lens should be around 90mm, and some other large-format cameras can also calculate the focal length of their standard lenses .

Wide-angle lens: a lens with a focal length of less than 35MM - when the focal length is smaller than the header, the lens can record images with a larger viewing angle, so it is called a wide-angle lens.The perspective of the wide-angle lens is exaggerated, presenting an obvious perspective effect of making the near bigger and the far smaller, emphasizing the sense of far and near, and it is often used in news photography and landscape photography, which will produce a strong visual impact.

Medium-focus lens: a lens with a focal length of 85MM to 135MM—a lens with a focal length 1.5 to 4 times larger than the focal length of the header, generally called a medium-focus lens. The photos taken at this focal length have the least distortion and can correctly reflect the shape of the subject. Moreover, it is relatively easy to design a large aperture. In portrait photography, the medium focal length is the most commonly used.

Telephoto lens: a lens with a focal length of more than 200MM - there is little sense of distance, and it has a compression effect on the perspective of the landscape.

The fixed focus lens of 135 camera (full frame) is as follows:

8mm fisheye: The photos taken are spherical images with a 180-degree field of view, and the distortion is extremely serious.

16mm fisheye: barrel-shaped deformation on the left and right, with a 180-degree field of view, suitable for large-scale shooting and exaggerated descriptions.

18mm super wide-angle lens: with a 100-degree field of view, it is suitable for shooting large scenes and exaggerated descriptions. When shooting at close range, the left and right sides will be deformed.

20mm ultra-wide-angle lens: 94-degree field of view, suitable for large-scale shooting and exaggerated descriptions. When shooting at close range, the left and right sides will be deformed.

24mm super wide-angle lens: 84-degree field of view, suitable for shooting large scenes.

28mm wide-angle lens: 74-degree field of view, suitable for general travel photos, landscape photos, documentary photography, etc.

30mm wide-angle lens: 70-degree field of view, suitable for general travel photos, landscape photos, documentary photography, etc.